Point Markers (Photometry)
The Point Markers page is a member of the
Aperture
Photometry Properties dialog. Use this page to configure the
marker placement and properties for objects being measured.
Point Marker Properties
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Mark Centroid
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Choose whether to locate the objects at a refined
centroid position rather than the exact point where you click.
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Positive
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If marking the centroid position, the centroid is
computed under the assumption that objects have positive brightness
above the background level.
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Negative
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If marking the centroid position, the centroid is
computed under the assumption that objects have negative brightness
below the background level.
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Radius
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Defines the distance from the target point within
which pixel data are used to compute the centroid position. A
reasonable starting point for choosing a value is 2 times the
FWHM.
(Note: FWHM measures a diameter and this parameter
is a radius).
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Tracking
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Defines the maximum distance from the current
position that Mira will search in the next image to lock onto a new
position. This is only used when tracking objects through an
Image Set.
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Track Centroid
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Check this option to calculate the centroid
position for each marker in each image.
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Calibrate when
Tracking
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Instructs Mira to compute and apply the zero point
to all objects when tracking through an image set. This is a time
saving feature that makes it unnecessary to follow Tracking by
Calibration as a separate step.
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Object Color
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Selects the color used for object markers.
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Standard Color
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Selects the color used for standard star
markers.
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Import Catalog
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Imports and processes a catalog containing
coordinate and photometric data from a text file as an alternative
to marking points manually. See the
Import Photometry Catalog tool.
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Reset Zero Point
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Resets the photometric zero point value.
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Recenter All
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Re centers the marked objects, usually done after
changing the marker centroid properties (see above).
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Report measurements in a
docking pane
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Check this box to report photometry measurements
in a private
docking pane of the
Image Window containing the aperture photometry
process. Uncheck this box to report measurements in a top level
Report Window. If you want to merge photometry
results from different windows into a single report, uncheck the
box.
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Centroiding on Positive and Negative Points
Centroid positions are computed using image data,
not the screen display. Choose Positivepoints or Negative points based upon the type of object to
measure rather than the palette or other image display properties.
For modern, inherently digital images, you will almost always
choose Positivepoints. However, when
working with a scanned photograph you may find that stars are
negative deviations from the background, so you would choose to
centroid on NegativePoints.
The Import Catalog button uses the
Import Photometry Catalog tool to load new
object coordinates into the aperture photometry session.
Save your changes
Set the Properties as desired, then accept the
changes by clicking [Apply].
Related Topics
Aperture Photometry
Aperture
Photometry Properties
Centroid Measurements,
Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All
Rights Reserved.
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